I have not seen any. Was thnking of doing it, but have not yet found the time (famous procrastinator).

No, John, I don't. I don't shoot Canon and don't have the tools to do it.

My question more more general in nature, though. If the two figures are different, how does one choose which to follow or which is better? I haven't compared figures for different cameras to see if or how the two may be different. But if the two present differing or contravening information on choosing the best max. ISO setting it would be helpful to know how to reconcile the two.

Jack, I'm thinking about trying to model this camera and compare it to the D800. Can you tell me the full well capacity and the unity gain ISO? The standard deviation of the ADU random noise would be nice -- I'll assume shot noise if you have no information. I'll assume the standard deviation of the pre-amp noise is that of shot noise, and I can calculate the pre-amp mean noise from your graph once I have the unity gain ISO.

Jim

Hi Jim,

Reading off the chart in the earlier post, FWC appears to be around 67500 e- and UG around 400. I get the curve in the graph assuming 8.4 ADU of random noise contributed by the amplifier at the output of the ADC. It's not bad but it's not a perfect fit to the calculated read noise. If I remember correctly the 5DIII has a couple of amplifying stages, which I treated as one in order to estimate this last figure.

No, John, I don't. I don't shoot Canon and don't have the tools to do it.

My question more more general in nature, though. If the two figures are different, how does one choose which to follow or which is better? I haven't compared figures for different cameras to see if or how the two may be different. But if the two present differing or contravening information on choosing the best max. ISO setting it would be helpful to know how to reconcile the two.

Sorry...misinterpreted you question.

Probably Jim Kasson would best to answer this. I could try, but would only be trying to interpret info he has provided me....and would probably do it poorly :-)

Q: How does one reconcile the Unity Gain ISO figures with the Photographic Dynamic Range Shadow Improvement?

Bob, I am no expert on unity gain, but I believe that Jim proved a few threads ago that Unity Gain is in practice only meaningful in very specific applications such as when one does heavy duty stacking for astrophotography. As far as I understand today PDR Shadow Improvement is as good as it gets in helping to make the proper SNR/DR compromise.

I, personally, just set my camera to full stop ISO. Since I shoot RAW only, I want to control whatever "ETTR" I am doing.

John

Ok, assuming that Bill's data for the 5DIII is correct and that you are shooting in full manual mode using the exposure/ISO strategy discussed in this thread, for maximum IQ and control you would want to keep doing what you are doing but always choosing ISO values 1/3 of a stop less than the standard ones (i.e. 159, 318, 636 etc. instead of 200, 400, 800...)

Reading off the chart in the earlier post, FWC appears to be around 67500 e- and UG around 400. I get the curve in the graph assuming 8.4 ADU of random noise contributed by the amplifier at the output of the ADC. It's not bad but it's not a perfect fit to the calculated read noise. If I remember correctly the 5DIII has a couple of amplifying stages, which I treated as one in order to estimate this last figure.

From his read noise numbers, I fitted a curve, and came up with a pre-gain read noise mean of 2.5 electrons, and a post-gain read noise mean of 7.5 ADC counts. This gave me a pretty good fit to his read noise data. I'm going to assume the variance of the two components of the read noise is the same as the mean (a la shot noise).

Then I'll do some modeling and see if the camera differences that people are talking about can be explained by the model parameters, or if there's something going on in the Canon that I'm not modeling.

However, the results may take me a day or two to generate. Some actual photography is intervening.

Ok, assuming that Bill's data for the 5DIII is correct and that you are shooting in full manual mode using the exposure/ISO strategy discussed in this thread, for maximum IQ and control you would want to keep doing what you are doing but always choosing ISO values 1/3 of a stop less than the standard ones (i.e. 159, 318, 636 etc. instead of 200, 400, 800...)

Jack

...or be in a mettered mode, with +1/3 EC...if i wanted to mimic the exposure of -1/3 ISO :-)

FWC: my figure comes out of the DxO full SNR curves - and they average the three channels (I am not sure whether they weigh them). Are Clark's derived just from the green channel? And I agree about the UG ISO: I had forgotten that Canon's Raw data is offset by a couple of thousand ADUs. 510 it is.

Quote

From his read noise numbers, I fitted a curve, and came up with a pre-gain read noise mean of 2.5 electrons

I can see that working if the OEM conversion utility were used. But it may not work with third party converters that don't pick all the tags.

majority of commercial 3rd party raw converter either are communicated by manufacturer or will know that from simple test or reverse engineering... some like RPP will not honor the tag intentionally, by design... so it is not an issue... and I guess at some point raw files from MFDB (PhaseOne) were like that ? just ISO by tag ?

Bob, I am no expert on unity gain, but I believe that Jim proved a few threads ago that Unity Gain is in practice only meaningful in very specific applications such as when one does heavy duty stacking for astrophotography. As far as I understand today PDR Shadow Improvement is as good as it gets in helping to make the proper SNR/DR compromise.

as it turned out the hidden expocorrection that Adobe's raw converters (ACR/LR) do is the sum of 2 values : one hardcoded in their code (that is what Adobe DNG converter shall reveal when you convert a native raw into Adobe's DNG) and another in their .dcp profiles

The metric that I've been using is photon-noise-corrected signal-to-noise ratio at a particular average value that corresponds to the shadow tone that you're most concerned about. I would think that this would be strongly correlated with PDR Shadow Improvement. However, I don't have enough information of the specifics of Claff's measurement of PDR Shadow Improvement to do a rigorous comparison. Any pointer would be appreciated.